Record storer utilizing hydraulically actuated means for positioning the writing and reading heads thereof

ABSTRACT

A record storer with selective control of the positioning or setting of the writing and reading heads thereof relative to the recording tracks of the recording carriers thereof, in which movement of such heads is effected by a linear hydraulic motor, with the flow of the hydraulic fluid to such motor being controlled through valves with variable flow characteristics, rough adjustment being effected by fluid flow through a first or through such a first and a second valve as a function of the difference between the actual position and the desired position, and fine adjustment being effected by fluid flow through said second valve in correspondence to the distance of the recording and reading heads from the desired track.

United States Patent 1 1 3,590,222-

[ 72] lnventors Peter Wentzel; [56] References Cited Manfred Becker, both of Munich, Germany UNITED STATES PATENTS [21] P M 837450 2,751,933 6/1956 Urtega 235/200 ux [22] F11ed June 27, 1969 45 P d J 29 1971 2,979,255 4/1961 Hubl 235/61.11J 2" "5cm 3,072,146 1/1963 Gizeski 235/200 x l 1 3,410,451 11/1968 Wilmer 235/61.11 J

Berlin and Munich, Germany [32] Priorit Jul 3,1968 Primary Examiner- Daryl W. Cook 33 Germany Anorneyl-lill, Sherman, Meroni, Gross & Simpson [31] Pl774502.7

ABSTRACT: A record storer with selective-control of the I positioning or setting of the writing and reading heads thereof [54] RECORDSTORER UTILIZING HYDRAULICALLY relative to the recording tracks of the recording carriers thereof, in which movement of such heads is efiected by a linear hydraulic motor, with the flow of the hydraulic fluid to such motor being controlled through valves with variable flow 6 Claims 2 Drawing Figs characteristics, rough adjustment being effected by fluid flow [52] U.S. Cl 2355/61., through a first or through such a first and a second valve as a 235/200 function of the difference between the actual position and the [51] Int. Cl ..Gllb 21/10, desired position, and fine adjustment being effected by fluid 606k 9/04 v flow through said second valve in correspondence to the [50] Field of Search 235/6111, distance of the recording and reading heads from the desired 61.1 1 J, 200, 201 track.

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SHEH 1 [IF 2 INVENTORS Wen/ze/ 6/6/ Wan/9" RECORD STORER UTILIZING I'IYDRAULICALLY ACTUATED MEANS FOR POSITIONING THE WRITING AND READING HEADS THEREOF BACKGROUND OF THE INVENTION The invention relates to a record storer with selective control of the positioning or setting of the writing and reading heads thereof relative to the recording tracks of the recording carriers thereof in which the movement of the writing and reading heads is accomplished by a linear hydraulic motor in which the flow of the hydraulic fluid to the cylinder chambers of the hydraulic motor is controlled by valves having variable flow characteristics.

Arrangements for the positioning of magnetic heads upon desired recording tracks in record storers are known in the prior art. Such positioning may, for example, be accomplished mechanically in which a motor actuates two sprocket wheels freely carried on respective shafts with the sprockets rotating in opposite directions and connectable, by means of respective magnetic couplings, to the corresponding shafts. An additional sprocket wheel on each shaft is operative to transmit movement to a belt associated therewith, such belt being adapted to fixedly support a guide which carries the respective magnetic heads. Also associated with the belt is a potentiometer adapted to be actuated by a pulley mounted on the operating shaft thereof which coacts with the belt whereby the potentiometer delivers a different resistance value for each position of the guide. The potentiometer is disposed in a branch of a bridge circuit whose output voltage is representative of the distance of the magnetic heads from the desired track and, depending on whether the output voltage is positive or negative, one of the magnetic couplings is actuated and the belts moved forward or rearward until the output voltage at the bridge circuit is zero (German Display Copy No. 1,129,736). This arrangement, however, has, in particular, the disadvantage of the impossibility of a rapid positioning of the magnetic heads.

In another known arrangement for positioning magnetic beads upon recording tracks of a record storer, all heads associated with the records are arranged for common rotation about a shaft extending parallel to the record actuating shaft and the heads are set to a selected track by rotation of the supporting shaft therefor through a certain angle by means of eccentrically positioned means until the heads have approximately reached the desired track. One side of each storage record carries time tracks placed on the same radii as the corresponding message tracks, which time tracks comprise two impulse lines recorded in side-by-side relation in opposite phase. The magnetic heads are in the selected position when the magnetic head scanning the time track is disposed between the corresponding impulse lines recorded in opposite phase (German Display Copy No. 1,074,887). As in the previously described arrangement, a rapid positioning of the magnetic heads upon a selected track is likewise impossible in this second arrangement. The problem solved by the invention is therefore the production of a record storer with a selectively controlled adjustment of the writing and reading heads upon the recording track, in which such setting or positioning is accomplished with maximum rapidity and maximum precision.

BRIEF SUMMARY OF THE INVENTION The problem of the invention is solved by the utilization of two regulators, each of which adjusts a respective valve for controlling a forward and a return movement of the carriage supporting the writing and reading heads, the flow through the valve set by the first regulator being controlled thereby as a function of the difierence of the actual track from the desired track, to effect a rough adjustment, and following completion of such rough adjustment, a precise setting of the recording and reading heads upon the desired track is effected by the second regulator controlling the flow through the cooperable valve, which is controlled in correspondence with the distance of the recording and reading heads from the desired track, to effect a fine adjustment.

The maximum flow through the valve controlled by the first regulator consequently can be made larger than the maximum flow through the valve controlled by the second regulator and thus depending upon which regulator is operative, the speed of movement of the recording and reading elements can be varied down to very small values. Furthermore, both regulators may be operated simultaneously to reduce the actual setting time for the coarse adjustment. It is also possible for the second regulator to take over the control of the recording and reading heads during the rough adjustment, for example, if the first regulator should fail.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which:

FIG. ll illustrates a basic circuit diagram of a control circuit embodying the invention; and

FIG. 2 is a chart illustrating the dependency, during the coarse adjustment, of the speed of the recording and reading heads on the distance between the actual and the desired tracks.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1 of the drawing, the reference numeral 10 designates a stack of records and the numeral 12 the recording and reading heads, such heads being mounted on a carriage 14 which may be reciprocated by means of a hydraulic system, the latter comprising a tank 16 containing hydraulic fluid, a pump 18, a pressure-limiting valve 20, valves 22, 24 and a cylinder 26 in which is disposed at double-acting piston 28 connected to the carriage 14. The respective valves control movement of the carriage forward or backward as a result of connection of fluid under pressure to the forward line 32 and the sump to the return line 30, or by connecting the pressure side to the return line 30 and the sump to the forward line 32.

To control movement of the recording and reading heads 12 to the desired track, determination of the present position of the recording and reading heads is accomplished by means of a so-called position indicator or position transmitter" 70, comprising a pair of conductors 72 and 76, which delivers an impulse whenever the recording and reading heads 12 pass over a recording track. The position indicator 70 may be designed similarly to a linear-inductosyn (Steinbuch Pocket Manual of Data Processing, Vol. 2, Page 1219). For example, the electrical conductor 72, hereinafter referred to as the transmission conductor" is disposed in a serpentine arrangement, may be positioned in fixed relation with respect to the stationary guide for the carriage I4 and thus the recording and reading heads 12, which conductor is connected to an AC source 74. The cooperable, similarly arranged conductor 76, hereinafter referred to as the receiving conductor" is disposed on the carriage 14 in close relation to the transmission conductor 72. The conductors 72 and 76 are so arranged that they can be disposed in superimposition and reciprocably movable relative to each other. If the transmission conductor 72 is connected to an AC source 74, and the receiving conductor 76 is displaced in relation to the transmission conductor 72, a voltage will be induced in the receiving conductor whose frequency corresponds to that of the AC source and whose peak amplitude values describe an approximately sinelike enveloping curve corresponding to the variation between the maximum and minimum coupling between the respective conductors as the latter are moved relative to one another at uniform speed. The induced voltage is amplified in I an amplifier 78 and then conducted to a phase-critical rectifier 80 which delivers the sinelike enveloping curve as a local stant when the output voltage has a value of zero.

The selectively controlled setting of the recording and reading heads 12 upon the desired track is determined by the selective operation of two regulators, with some components of the respective control circuits therefor being utilized in common. The first regulator control circuit includes the position indicator 70, a track difference register 50, a track decodin'g circuit 52, a digital-analog converter 54, and a differential amplifier 56, the outputs of which are connected directly to the valve 22.

The second regulator control circuit includes the position indicator 70, a second digital-analog converter 58, which also functions as a switch, and a differential amplifier 60, whose outputs are connected to the valve 24. Control means 90 also may be provided which may form a part of a data processing system. i I

The operation of the control system is as follows:

At the beginning of the control operation, the differential address indicating the difference between the actual and the desired tracks is supplied to the track differential register 50, and at the same time it is determined in control means 90 whether such difference is positive or negative. Depending on the polarity of such difference, a corresponding signal is produced and transmitted therefrom over the digital-analog converter 54, and/or analog-digital converter 58, functioning as a switch, and over the differential amplifier 56,60 to valves 22,24, whereby the valves are actuated for forward or reverse operation. The control lines for the forward operation is identified by' the letter V and the control lines for the reverse operation by the letter R.

The contents of the track difference register 50 is con ducted over the track decoding circuit 51 to the digital-analog converter 54 where the digital value of the track difference register is converted into an analog potential signal controlling the differential amplifier 56. Depending upon whether the difference in the track difference register 50 is negative or positive, the valve 22 is set by the output of the differential amplitier 56 for forward or return operation whereby hydraulic fluid is pumped through the feed lines 32 or 30. Such hydraulic fluid moves the piston 28 in the cylinder 26 and thus reciprocates the carriage l4 and the recording and reading heads 12 thereon into and/or out of the record stack, whereby such heads pass over the recording tracks on the recording carriers. Whenever such a recording track is passed over, the position indicator 70 delivers an impulse which is fed to the track difference register 50 whereby the value contained therein is reduced by one. As the difference drops, the digitalanalog converter delivers a signal which becomes smaller and smaller, operative over the differential amplifier 56 to reduce the flow through valve 22 until it eventually becomes zero, when the track difference register has counted down to zero.

Consequently, the speed of the recording and reading heads 12 is shifted downward as a function of the difference contained in the track difference register 50. This dependency is programmed with the aid of the track decoding circuit and the digital-analog converter circuits, and may be termed the brake program. The dependency between the speed v and the track difference f is represented in the diagram of HO. 2, which shows that the speed is gradually reduced as the track difference becomes smaller. The number of steps is determined by the difference contained in the track difference register 50, and if the track difference is for example, the contents of the track difference register is changed 10 times as such number of steps are produced in which the speed is adjusted downward. The track decoding circuit 52 is provided to enable a limiting of the number of such steps, whereby the brake program can be so determined thereby that down to a predetermined path difference the carriage 14 travels at a constant speed and when the difference drops below such value, the speed is thereafter regulated downwardly in a series of steps.

When the value in the track difference register 50 has become equal to'zero, control by the first regulator is terminated, which control may be termed the rough-adjustment, and obviously utilizes a path-responsive speed control.

The precise control of the recording and reading head 12 with respect to the desired track is effected by the second regulator associated with the valve 22. If the content of the track difference register 50 is zero, the digital-analog converter 58 actuates the second regulator, with the control now taking place proportionately, i.e. the differential amplifier 60 steadily varying the flow of the valve controlled thereby and not in steps. The control thus takes place according to the local function, of sinelike configuration, delivered by the phase-critical rectifier 80. As long as the recording and reading heads 12 are not disposed directly over the desired track, the amplitude value of the local function is a value other than zero, and the second regulator adjusts the speed of movement of the carriage 14 in accordance with such amplitude value. Thus, the latter value is a measurement of the distance of the reading and recording heads 12 from the desired track and the closer the reading and recording heads 12 approach such desired track, the smaller the amplitude value becomes, and the smaller the voltage delivered by the differential amplifier 16, resulting in a reduction of the flow through the valve controlled by such amplifier. Each zero point of the local function corresponds to a recording track scanned by the reading and recording heads and, depending upon whether the absolute address of the recording track placed in a track address register 94 is odd or even, a positive increase of the local function or a negative increase of the local function would be supplied to the difierential amplifier 60 as voltage for controlling the writing and reading heads 12 upon the actual track, which in the second case can cause an instability of the control. To prevent this, the polarity of the local function in the phasecritical rectifier is reversed by the track address register 94, operative over line 92, which thus corresponds to a phase shift of H30. This assures that positive increasing values of the local function are always supplied to the differential amplifier 60 regardless of whether the contents of the track address register 94 are odd or even. If the recording and reading heads 12 actually are directly positioned above the desired track, the local function is zero, no voltage is present at the differential amplifier 60 and the control operation is completed. The control of the recording and reading heads 12 by the second regulator thus comprises a fine adjustment and is a position control.

To reduce the time required for the rough adjustment, it is possible to effect a simultaneous operation of both valves during such rough adjustment, in which case the second valve is shifted by the digital-analog converter to digital control and completely controlled thereby, such shifting by the digitalanalog converter 58 to the corresponding local function taking place only after completion of the rough adjustment. This also is particularly advantageous in the event of a failure of the first regulator, as the second regulator can then take over the sole control of the movement of the recording and reading heads during coarse adjustment as well as during fine adjustment.

As the maximum flow through the valve 24, controlled by the second regulator, normally will be small in relation to the maximum flow through the valve 22 controlled by the first regulator, it may in such case be fully open during the rough adjustment and requires no brake program.

What we claim is:

l. A record storer having a selectively controllable setting of the recording and reading heads upon the recording tracks of the recording carriers, in which the movement of such recording and reading heads is accomplished by a linear hydraulic motor, the combination of a pair of valves having variable flow characteristics, for controlling fluid flow to said motor, a pair of regulators, each of which adjusts one of said valves for forward or reverse flow, means for controlling a first of said regulators whereby the valve set thereby is controlled as a function of the amount of the difference between the actual track position of the recording and reading heads and the desired track position thereof to effect a rough adjustment, and means operative after completion of said rough adjustment for controlling the second of said regulators whereby the flow through the valve set thereby is controlled in correspondence with the distance of the recording and reading heads from the desired track to effect a precise fine adjustment of said head with respect to the desired track.

2. A record storer according to claim 1, wherein the first regulator controlling means comprises a position indicator which is operable to transmit an impulse whenever the recording and reading heads pass over a recording track, a track difference register connected to said position indicator and constructed to contain the amount of the difference between the desired track and the actual track passed over by the recording and reading heads, a digital-analog converter operatively connected to said difference register, and a differential amplifier operatively connected to said converter and said first regulator, the output voltage of said amplifier varying gradually in accordance with the contents of the track difference register whereby said first regulator is operative to effect a variation in the fluid flow to said first valve as the contents in said difference register approaches zero.

3. A record storer according to claim 1, wherein the second regulator controlling means includes a position indicator, which is operable to deliver a sine-shaped signal having a zero value whenever the recording and reading heads pass over a recording track, a digital-analog converter, means operatively connecting the latter to said position indicator, and a differential amplifier, operatively connected to said converter and said second regulator, the output of which is operative following the rough adjustment to control adjustment of said second valve.

4. A record storer according to claim 1, wherein the first regulator controlling means comprises a position indicator which is operable to deliver a sine-shaped signal having a zero value whenever the recording and reading heads pass over a recording track, and to transmit an impulse whenever the recording and reading heads pass over a recording track, a track difference register connected to said position indicator and constructed to contain the amount of the difference between the desired track and the actual track passed over by the recording and reading heads, a digital-analog converter operatively connected to said difference register, and a differential amplifier operatively connected to said converter and said first regulator, the output voltage of said amplifier varying gradually in accordance with the contents of the track difference register whereby said first regulator is operative to effect a variation in the fluid flow to said first valve as the contents in said difference register approaches zero, the second regulator controlling means including said position indicator, a second digital-analog converter, means operatively connecting the latter to said position indicator, and a differential amplifier, operatively connected to said converter and said second regulator, the output of which is operative following the rough adjustment to control adjustment of said second valve.

5. A record storer according to claim 4, wherein said second regulator is operative to fully open the valve associated therewith whereby the latter is connected on the output side in parallel with the valve controlled by said first regulator during the rough adjustment.

6. A record storer according to claim 1 or 4, wherein said valves are so constructed that the maximum flow through the valve controlled by the first regulator is larger than the maximum flow through the valve controlled by the second regulator. 

1. A record storer having a selectively controllable setting of the recording and reading heads upon the recording tracks of the recording carriers, in which the movement of such recording and reading heads is accomplished by a linear hydraulic motor, the combination of a pair of valves having variable flow characteristics, for controlling fluid flow to said motor, a pair of regulators, each of which adjusts one of said valves for forward or reverse flow, means for controlling a first of said regulators whereby the valve set thereby is controlled as a function of the amount of the difference between the actual track position of the recording and reading heads and the desired track position thereof to effect a rough adjustment, and means operative after completion of said rough adjustment for controlling the second of said regulators whereby the flow through the valve set thereby is controlled in correspondence with the distance of the recording and reading heads from the desired track to effect a precise fine adjustment of said head with respect to the desired track.
 2. A record storer according to claim 1, wherein the first regulator controlling means comprises a position indicator which is operable to transmit an impulse whenever the recording and reading heads pass over a recording track, a track difference register connected to said position indicator and constructed to contain the amount of the difference between the desired track and the actual track passed over by the recording and reading heads, a digital-analog converter operatively connected to said difference register, and a differential amplifier operatively connected to said converter and said first regulator, the output voltage of said amplifier varying gradually in accordance with the contents of the track difference register whereby said first regulator is operative to effect a variation in the fluid flow to said first valve as the contents in said difference register approaches zero.
 3. A record storer according to claim 1, wherein the second regulator controlling means includes a position indicator, which is operable to deliver a sine-shaped signal having a zero value whenever the recording and reading heads pass over a recording track, a digital-analog converter, means operatively connecting the latter to said position indicator, and a differential amplifier, operatively connected to said converter and said second regulator, the output of which is operative following the rough adjustment to control adjustment of said second valve.
 4. A record storer according to claim 1, wherein the first regulator controlling means comprises a position indicator which is operable to deliver a sine-shaped signal having a zero value whenever the recording and reading heads pass over a recording track, and to transmit an impulse whenever the recording and reading heads pass over a recording track, a track difference register connected to said position indicator and constructed to contain the amount of the difference between the desired track and the actual track passed over by the recording and reading heads, a digital-analog converter operatively connected to said difference register, and a differential amplifier operatively connected to said converter and said first regulator, the output voltage of said amplifier varying gradually in accordance with the contents of the track difference register whereby said first regulator is operative to effect a variation in the fluid flow to said first valve as the contents in said difference register approaches zero, the second regulator controlling means including said position indicator, a second digital-analog converter, means operatively connecting the latter to said position indicator, and a differential amplifier, operatively connected to said converter and said second regulator, the output of which is operative following the rough adjustment to control adjustment of said second valve.
 5. A record storer according to claim 4, wherein said second regulator is operative to fully open the valve associated therewith whereby the latter is connected on the output side in parallel with the valve controlled by said first regulator during the rough adjustment.
 6. A record storer according to claim 1 or 4, wherein said valves are so constructed that the maximum flow through the valve controlled by the first regulator is larger than the maximum flow through the valve controlled by the second regulator. 